Development and control of a compliant asymmetric antagonistic actuator for energy efficient mobility

This paper presents the development and control of a novel asymmetric antagonistic actuation scheme characterized by large energy storage capacity that enables efficient execution of motions. The asymmetric design consists of two actuation branches that transfer their power to a single joint through two compliant elements with different stiffness and storage capacity properties. The guideline for selecting the stiffness of both elements is elaborated, given the design parameters and control requirements. We propose a novel control strategy that distributes the effort required to generate the motion using the two actuation branches of this novel hardware, to drive the prototype joint in an energy efficient manner. As a proof of concept, a single degree-of-freedom knee-actuated hopping robot is designed for experimental validation. The dynamics of the leg and actuators are rigorously modeled and formulated. The data from simulation and experimental studies demonstrate a significant improvement in electrical energy efficiency and reduction in torque requirements.